Abstract. An investigation of the Planetary Boundary Layer (PBL) height evolution over
Greece, during the solar eclipse of 29 March 2006, is presented. Ground
based observations were carried out using lidar detection and ranging
devices and ground meteorological instruments, to estimate the height of the
mixing layer (ML) before, during and after the solar eclipse in northern and
southern parts of Greece exhibiting different sun obscuration. Data
demonstrate that the solar eclipse has induced a decrease of the PBL height,
indicating a suppression of turbulence activity similar to that during the
sunset hours. The changes in PBL height were associated with a very shallow
entrainment zone, indicating a significant weakening of the penetrative
convection. Heat transfer was confined to a thinner layer above the ground.
The thickness of the entrainment zone exhibited its minimum during the
maximum of the eclipse, demonstrative of turbulence mechanisms suppression
at that time. Model estimations of the PBL evolution were additionally
conducted using the Comprehensive Air Quality Model with extensions (CAMx)
coupled with the Weather Research and Forecasting model (WRF).
Model-diagnosed PBL height decrease during the solar eclipse due to vertical
transport decay, in agreement with the experimental findings; vertical
profiles of atmospheric particles and gaseous species showed an important
vertical mixing attenuation.